For instance, the parking lock device for the conventional gear type transmission is disclosed in the Japanese Patent Application Laid-Open No. 9-295561. Lock mechanism which has a lock lever which engages with the parking gear when the engine is stopped and disengages with the parking lock when the engine is operated, an actuator which operates this lock lever, and a control means which operates this lock mechanism are provided in the device described in this patent gazette. The lock mechanism is operated when the engine is at an off state, and the rotation of the parking gear is prevented automatically. Therefore, even when the operation of a side brake to the position where the vehicle is parked is uncertain, the vehicle can be prevented from moving in contradiction to the intention. There is a problem that the configuration of the transmission is complicated, and its weight is also increased because the parking lock device to lock the vehicle when parking must be newly provided with some components separately in the gear type transmission as mentioned above.